In recent years, for example, in Europe and North America, installation of daytime running lights, which are being switched on all the time, in automobile head lamps and rear lamps has been promoted to increase the conspicuity from pedestrians and cars in the opposite lane during the daytime. Such daytime running lights generally include a light guide member and a light source that emits light incident on the light guide member. In general, incandescent lamps such as halogen lamps are disposed as typical light sources for the nighttime near the daytime running lights of automobiles. The light guide member is heated by heat generated from the light sources of the daytime running lights and heat generated from the incandescent lamps. Therefore, the light guide member needs to have excellent thermal resistance.
For example, PTL 1 discloses, as a material for light guide members, an aromatic polycarbonate resin composition obtained by adding a phosphorus-based stabilizer and a fatty acid ester to an aromatic polycarbonate resin. When a known aromatic polycarbonate resin composition is molded to produce a light guide member for automobile lighting devices, the aromatic polycarbonate resin deteriorates because of heat during the molding process and the produced molded article may have a slight tinge of yellow. Furthermore, even if the light guide member does not have a tinge of yellow during the molding, the light guide member deteriorates and turns yellow by being exposed to heat from a light source around the light guide member for a long time.
PTL 2 discloses an aromatic polycarbonate resin composition that improves yellowing resistance and inhibits yellowing even when exposed under heating conditions for a long time. The aromatic polycarbonate resin composition is obtained by adding two phosphite stabilizers and a fatty acid ester to an aromatic polycarbonate resin.
PTL 1: Japanese Patent Publication 2007-204737 A
PTL 2: Japanese Patent Publication 2015-189879 A
Light guide members incorporated in automobile lighting devices are desirably formed of a material that has a better hue and thermal yellowing-inhibiting effect than known aromatic polycarbonate resin compositions.